DE102013204540A1 - Battery cell device with depth discharge safety function and method for monitoring a battery cell - Google Patents

Abstract

The present invention relates to a battery cell device (221) with a battery cell (21) and a monitoring device, which uses a sensor device (240) for detecting a plurality of physical variables relating to the battery cell (21), a state determination device (250) an evaluation of current measured values of the physical quantities provided by the sensor device (240) to recognize a battery cell state, and an actuator device (260) which is designed to transfer and / or to keep the battery cell from a critical battery cell state to a safe operating mode, includes. A deep discharge safety function (270) is preferably provided, by means of which a critical battery cell state in which the battery cell (21) can be damaged by a deep discharge can be determined by the state determination device. In the presence of the critical battery cell state, the battery cell (21) can be transferred by the actuator device (260) into a deep discharge operating mode designed as a safe operating mode, in which the battery cell (21) cannot be further discharged or can be completely discharged.

Description

Field of the invention

The present invention relates to a battery cell device having a battery cell and a monitoring device for monitoring the battery cell. The invention further relates to a corresponding method for monitoring the battery cell arranged in a battery cell device by means of the monitoring device arranged in the battery cell device. The invention also relates to a battery system with at least one such battery cell device. Furthermore, the invention relates to a vehicle with such a battery system

State of the art

It is common to refer to batteries for use in hybrid and electric vehicles as traction batteries, as these batteries are used for the supply of electric drives. In order to achieve the performance and energy data required for hybrid and electric vehicles, individual battery cells are connected in series and sometimes additionally in parallel in the traction batteries used. In electric vehicles often 100 battery cells or more are connected in series, the traction batteries have voltages of up to 450 V. Even in hybrid vehicles, the voltage limit of 60 V is usually exceeded, which is still classified as uncritical when touched by people.

In the 1 is the schematic diagram of a battery system 10 with such a traction battery 20 shown. The battery 20 includes several battery cells 21 , To simplify the illustration from the 1 were only two battery cells by the reference numeral 21 Mistake.

The battery 20 is from two battery cell series circuits 22 . 23 formed, each having a plurality of battery cells connected in series 21 include. The battery cell series circuits 22 . 23 are with their connections each with a battery terminal 24 . 25 and a connection of a service connector 30 connected. The positive battery terminal 24 is with the battery 20 via a separating and charging device 40 connectable, which is a circuit breaker 41 comprising, connected to a series connection of a charging switch 42 and a charging resistor 43 is connected in parallel. The negative battery terminal 25 is with the battery 20 via a separating device 50 connectable, which is another disconnector 51 includes.

2 shows a diagram 60 that the fault mechanisms of lithium ion batteries and their consequences 62 is very schematic. The illustrated malfunction mechanisms can be caused by an inadmissible increase in temperature 63 induced thermal runaway (thermal runaway) 64 the battery cells 21 to lead. In the presence of a thermal runaway 64 There may be an issue from the gas 65 , which may occur, for example, when opening a burst valve as a result of increased battery cell internal pressure, to a burning 66 the battery cells, or even bursting in extreme cases 67 the battery cells 21 come. Therefore, the occurrence of thermal runaway must be 64 in the use of battery cells 21 be excluded in traction batteries with a high probability close to 1.

A thermal runaway 64 can be overcharged 70 a battery cell, as a result of a deep discharge 80 a battery cell 21 during the subsequent charging process or in the presence of impermissibly high charging and discharging currents of the battery cell 21 , for example, in the presence of an external short circuit 90 can arise, occur. Furthermore, a thermal runaway 64 even in the presence of a battery cell internal short circuit 100 occur, for example, as a result of a strong mechanical force during an accident 101 or as a result of the formation of battery cell internal dendrites 102 may arise, for example, in the presence of excessive charging currents at low temperatures. Furthermore, a thermal runaway 64 also occur as a result of battery cell internal short circuits caused by in the manufacturing impurities of the battery cells 21 , in particular by in the battery cells 21 existing metallic foreign particles 103 , can be caused. Also, a thermal runaway 64 in the presence of an impermissible heating of the battery cells 21 , which may arise, for example, as a result of a vehicle fire, or in the presence of an overload 120 the battery cells 21 occur.

For lithium-ion battery cells, safety tests are mandatory. To the battery cells 21 For example, UN transport tests must be carried out. The test results must be assessed according to the EUCAR Hazard Levels (EUCAR Hazard Levels). The battery cells 21 must comply with given minimum safety levels. To achieve this, are in the battery cells 21 , which are designed for use in traction batteries, taken extensive additional measures. Such additional measures are taken by integrating so-called safety devices in the battery cells. Typically, the safety devices listed below are integrated.

In a battery cell 21 An Overcharge Safety Device (OSD) will be integrated. Such a Überladesicherheitsvorrichtung causes that the battery cell 21 during an overcharge, an EUCAR hazard level 4 does not exceed. The permissible range of the battery cell voltage ends at 4.2 V. During an overcharging process, the battery cell builds 21 from a battery cell voltage of about 5 V to such a high internal pressure, which is arched a membrane of the overcharge safety device to the outside and the battery cell 21 electrically shorts. As a result, the battery cell becomes 21 until a battery-internal fuse is activated. The short circuit of the battery cell 21 between the two battery cell terminals remains over the Überladesicherheitsvorrichtung.

In a battery cell 21 Furthermore, a battery cell fuse (Cell Fuse) is integrated. This in the battery cell 21 Integrated fuse is a very effective battery cell level protection device, but causes considerable problems in the installation of the battery cells 21 in a series connection of a battery module or in a battery system. There, these measures are rather counterproductive.

In a battery cell 21 Also, a Nail Penetration Safety Device (NDS) is integrated. This nail penetration safety device protects the battery cell 21 , by penetrating a nail in the battery cell 21 a defined short circuit path is established, which does not lead to a strong local heating of the battery cell in the area of the nail entry, which could lead to a local melting of the existing separator.

In a battery cell 21 A functional safety layer (SFL) is also integrated. The functional safety layer is realized by the ceramic coating of one of the two electrodes, preferably by the ceramic coating of the anode. By means of the functional safety layer, when the separator melts, a flat short-circuit of the battery cell can occur 21 and thus an extremely fast conversion of the electrical energy of the battery cell 21 be prevented in lost heat.

In a battery cell 21 Furthermore, a shock safety device (Crush Safety Device) is integrated. The shock safety device has a similar operation as the nail penetration safety device. With a strong mechanical deformation of the battery cell case becomes a defined short circuit path in the battery cell 21 provided a strong local heating of the battery cell 21 prevents and thereby the safety of the battery cell 21 elevated.

For the battery cells currently under development 21 In particular, the measures for electrical safety, for example, protect against overcharging or ensure overcurrent protection, associated with considerable effort. These measures are also after the installation of a battery cell 21 in a battery module or in a battery system rather counterproductive than useful. For example, upon activation of the fuse of a battery cell 21 The situation arises that the electronics of the existing battery management system (BMS) is exposed to very high negative voltages. This results in an additional effort on the battery system level, which is caused because the transport regulations must be met at the battery cell level without any benefit associated with it.

In the 3 is the block diagram of a known from the prior art battery system 10 shown that a traction battery 20 with several battery cells 21 and a battery management system. The electronics of the battery management system (BMS) has a decentralized architecture in which the from the monitoring electronics (CSC electronics) of the battery cells 21 trained cell monitoring units 130 are designed as satellites, for monitoring the functional state of one or more battery cells 21 are each formed and via an internal bus system 141 with a central battery control unit (BCU) 140 communicate.

The electronics of the battery management system, in particular the monitoring electronics of the battery cells 21 , is required to the battery cells 21 before the critical, in the 2 Protected states that can lead to a thermal runaway. In the electronics of the battery management system, a high effort is operated, on the one hand, the battery cells 21 to protect against overload by external causes, such as by a short circuit in the inverter of an electric drive, and not by a malfunction of the electronics of the battery management system, such as by a faulty detection of the battery cell voltages by the cell monitoring units 130 , to endanger.

Just like the one in the 1 illustrated battery system 10 is in the in the 3 illustrated battery system 10 the traction battery 20 with a positive battery terminal 24 via a separating and charging device 40 connectable and with a negative battery terminal 25 via a separating device 50 connectable. For the designation of the same components in the 1 and 3 The same reference numerals have been used here.

Further, the central battery control device 140 adapted to disconnect (relay) 41 and the charging switch (relay) 42 the separating and charging device 40 head for. The activation of the disconnector 41 and the charging switch 42 by means of the battery control device 140 is with the arrow 142 symbolizes. Also is the central battery control unit 140 adapted to the other disconnector (relay) 51 the separator 50 head for. The activation of the disconnector 51 by means of the battery control device 140 is with the arrow 143 symbolizes.

The central battery control unit 140 is in each case via a high-voltage line 144 . 145 with a different battery terminal 24 . 25 connected. Furthermore, the central battery control device comprises 140 current sensors 150 . 160 that are designed by the traction battery 20 to measure flowing electricity. The battery control unit 140 also communicates with a vehicle interface via a CAN bus 146 , Via the CAN bus, the battery control unit can 140 Information about the functional state of the vehicle can be provided.

With a battery management system of a battery system known from the prior art is sought, the safety of the battery system 10 to increase so that no unreasonable risk occurs. It will be in accordance with the ISO 26262 high demands on the functional safety of the battery management system, as a malfunction of the electronics can pose a threat. For battery management systems in electric vehicles and plug-in hybrids (plug-in hybrids), a classification according to the danger level ASIL C is expected to establish if the safety of the battery cells 21 can not be significantly increased.

Disclosure of the invention

According to the invention, a battery cell device is provided with a battery cell and a monitoring device for monitoring the battery cell. In this case, the monitoring device comprises a sensor device for detecting a plurality of physical variables relating to the battery cell, a state determining device which is designed to detect a current and / or future battery cell state based on a particular model-based evaluation of the current physical value measurements provided by the sensor device or predict and an actuator device configured to transfer and / or maintain the battery cell from a critical and / or critical battery cell state to a safe mode of operation. Furthermore, the monitoring device preferably provides a deep discharge safety function, by means of which a critical battery cell state in which the battery cell can be damaged by a deep discharge can be determined by the state determination device and the battery cell in the presence of the critical battery cell state by the actuator device in a defined as safe operation mode depth discharge operating mode in which the battery cell can not be discharged further, or can be completely discharged, transferred and / or held.

The invention further provides a method for monitoring a battery cell arranged in a battery cell device by means of a monitoring device arranged in the battery cell device. In this case, a plurality of physical variables for determining a battery cell state are detected by means of a sensor device arranged in the monitoring device and a current and / or future battery cell state detected by means arranged in the monitoring device state detection device based on a particular model-based evaluation provided by the sensor device current measurements of physical quantities and / / or predicted. Furthermore, in the presence of a critical and / or critical battery cell state, the battery cell is transferred into a safe operating mode by means of an actuator device arranged in the monitoring device. Furthermore, the monitoring device preferably provides a deep discharge safety function by means of which the occurrence of a critical battery cell state in which the battery cell can be damaged by a deep discharge is determined by the state determination device, wherein in the presence of the critical battery cell state, the battery cell by the actuator device as a safe Operating mode designed depth discharge mode in which the battery cell is not further discharged or completely discharged, transferred and / or held.

The dependent claims show preferred developments of the invention.

Thus, a battery cell device is provided with a battery cell and a monitoring device or monitoring electronics according to the invention. The monitoring electronics according to the invention can also be integrated in the battery cell. A battery cell with integrated monitoring electronics according to the invention is also referred to below as (electrically) intrinsically safe battery cell.

An electrically intrinsically safe battery cell comprises an electrochemical battery cell, in particular an electrochemical lithium-ion battery cell, a sensor system for detecting physical quantities for determining the state of the battery cell, a battery state detection and prediction device determining the current state from the sensor signals the battery cell (battery cell state) determined in particular with regard to their safety and predict the future behavior of the battery cell (predict), and a safety actuator (actuator device), with the battery cell when recognizing a critical condition and / or operation of the battery cell when needed in a safe operating state can be transferred.

Furthermore, safety functions, in particular a deep discharge safety function, are preferably integrated in the intrinsically safe battery cell, which immediately convert the battery cell into a safe operating mode in the presence of a critical or critical battery cell state. The deep discharge safety function is used here for avoiding a deep discharge of the battery cell and / or for safe operation of a battery cell in which a deep discharge has occurred.

The battery cell is carried out so securely in particular in connection with the depth discharge safety function presented here that the requirements for the electronics of a higher-level battery management system, in particular with respect to avoiding a deep discharge of a battery cell and / or with respect to the operation of a battery cell, in which a depth discharge has occurred, compared to State of the art can be significantly reduced.

The intrinsically safe battery cell can protect itself against impermissible operating states, without having to depend on the function of the electronics of a higher-level battery management system. An intrinsically safe battery cell provides a basic building block from which safe battery systems can be constructed in a simple manner. Thus, the security can be significantly increased in particular of large battery systems, such as those used for example in electric and hybrid vehicles.

In addition, the current non-targeted measures for the electrical safety of the battery cell, such as the provision of the battery cell with an overcharge safety device (Overcharge Safety Device) or a battery cell fuse (Cell Fuse) eliminated. Also, for example, by providing the battery cell with a Nail Penetration Safety Device NSD measures to increase the security of strong mechanical force effects, for example, in penetration of the battery cell with sharp objects, which is simulated by the Nail Penetration Test (Nail Penetration Test), and occur at high deformation of the battery cell, which are simulated by the impact tests (crush tests) in the three spatial axes, can be eliminated or at least much easier to implement, since the requirements are lower by the battery cell.

In a particular embodiment of the battery cell device according to the invention, the sensor device is designed to detect the battery cell voltage and / or to monitor the presence of a battery cell voltage whose magnitude is in a predetermined battery cell voltage range. Furthermore, the sensor device is preferably configured to generate a current flowing through the battery cell and / or a battery cell temperature, in particular a battery cell temperature and / or a battery cell temperature and / or a battery cell external temperature, and / or a battery cell internal pressure and / or a linear acceleration of the battery cell and / or detect a spin of the battery cell. Furthermore, the actuator device is preferably designed to activate an unloading device arranged in the battery cell for transferring the battery cell into the safe operating mode and / or for holding the battery cell in the safe operating mode. In this case, the discharge device is provided to discharge the battery cell in an activated discharge mode by means of a predetermined discharge current and / or in an activated fast discharge mode by means of such a discharge current, which is a predetermined fraction of a short-circuit current of the battery cell. The actuator device is also preferably designed to activate a current bypass arranged in the battery cell device. The current bypass is intended, in the activated state, to divert a current flowing between the battery cell terminals via a current path lying outside the battery cell.

In other words, the following sensor elements are used to detect the battery condition in the sensor device or sensor system.

The sensor device preferably initially comprises a battery cell voltage detection, by means of which the output voltage of the electrochemical battery cell is detected. Optionally, this battery cell voltage detection can be supplemented by a voltage range control, which is used to monitor whether the battery cell voltage within the specified allowable range, for example, between 2.8V to 4.2V.

Furthermore or alternatively, the sensor device preferably comprises a battery cell current detection, with which the electric current is detected by the electrochemical battery cell, and / or a battery cell temperature detection, with which the temperature of the electrochemical battery cell is detected. Particularly interesting is the temperature of the cell coil. If necessary, the outside temperature and the inside temperature of the battery cell can be detected.

The sensor device preferably also comprises, alternatively or additionally, a pressure sensor with which the internal pressure of a battery cell, in particular a lithium-ion battery cell with a hard-shell housing (hardcase housing), is detected.

Furthermore, the sensor device preferably comprises alternatively or additionally acceleration sensors for the three spatial axes for detecting linear accelerations of the battery cell. Other sensor elements may be required depending on the battery cell technology or may be useful to improve the accuracy or reliability of the battery state detection and to predict a safety-related operation or state of the battery cell can. Thus, for example, the use of rotation rate sensors (rotational acceleration sensors) may be useful to detect a driving dynamics critical situation and early to initiate the transfer of the battery cells in a safe even in the event of an accident operating mode.

From the sensor element signals for voltage, current, temperature, and internal pressure of the battery cell can be determined by means of a battery condition detection according to the invention, whether the battery cell is in a critical state or will come into a critical state. For the battery state detection and prediction model-based methods or evaluations can be used advantageously.

Furthermore, the actuator device or the safety actuator is designed to restore the battery cell to a safe state or to keep it in a safe area.

For this purpose, the security of the battery cell, in particular a lithium-ion battery cell is preferred to be able to discharge the battery cell. The requirements for the discharge currents to be realized depend on the battery cell chemistry used and the worst case operating conditions and worst case misuse conditions or worst case abuse conditions to which the battery cell can be exposed ,

In many cases, it will be advantageous to form the discharge device with an Ultra Fast Discharge Device (UFDD) or with a fast discharge mode in order to obtain the cell in a particularly reliable manner intrinsically safe. With a quick discharge device, the battery cell can be quickly discharged with very high discharge currents near the short-circuit current.

The possibility for discharging the battery cell is for the realization of an intrinsically safe battery cell, in particular a lithium-ion battery cell, preferably a necessary condition.

Furthermore, the security actuator for the realization of an intrinsically safe battery cell, in particular a lithium-ion battery cell, preferably in a position to switch a current bypass for the battery cell or to activate. A current can flow between the two battery cell terminals or output terminals via the current bypass, without the current flowing through the electrochemical battery cell. The current bypass is preferably capable of being able to carry currents of both polarities.

In a particularly advantageous embodiment of the battery cell device according to the invention, the state detection device is adapted to the critical battery cell state in which the battery cell can be damaged by a deep discharge, in the presence of an amount of battery cell voltage and / or an amount of battery cell arrest voltage and / or a battery cell charging state, respectively reaches or falls below a first corresponding limit value and / or exceeds a threshold value that is smaller than the second corresponding limit value and, in particular, set as a function of the requirements for the availability of the battery cell, to be determined. Furthermore, the actuator device is preferably designed to activate the current bypass in a state in which a discharge current would flow through the battery cell, and the current bypass, in another state in which a charging current flows through the battery cell in order to transfer the battery cell into the deep discharge operating mode can, disable.

In other words, the battery cell is discharged during normal operation until the voltage the battery cell (battery cell voltage) has reached the lowest limit value (the first limit value for the battery cell voltage) allowed according to the specification U _min . Alternatively, the deep discharge safety function can also be carried out for the state of charge of the battery cell (battery cell charge state) SOC or the rest voltage U _{00 of} the battery cell (battery cell arrest voltage). These state variables of the battery cell are determined by means of the battery state detection and prediction (state determination device).

As long as a discharge current (i <0) flows through the electrochemical part of the battery cell, the current bypass is activated. The battery cell is thus not discharged further. Furthermore, as soon as a charging current (i> 0) can flow through the electrochemical part of the battery cell, the current bypass is deactivated again. The battery cell is then recharged. The described and provided within the depth discharge function of the invention activations and deactivations of the current bypass are performed as long as the battery _{cell is} in a range U _{min_safety} <U _{battery cell} <U _min . If the battery cell in its battery cell voltage value U below _min, it can, for example, by self-discharge (about 1% -3% per month) after a very long storage without charging drop so far in their battery cell voltage to the limit value U _{min_safety} (the second Limit for the battery cell voltage) is below.

In a further preferred embodiment of the battery cell device according to the invention, the state detection device is adapted to the critical battery cell state in which the battery cell can be damaged by a deep discharge, in the presence of an amount of the battery cell voltage and / or an amount of Batteriezellenruhespannung and / or a battery state of charge, respectively falls below the second corresponding limit. Furthermore, the actuator device is preferably designed to permanently activate the current bypass for activating the battery cell in the depth discharge mode in the presence of the critical battery cell state and / or to activate the unloading device. The battery cell can then be completely discharged via the suitably activated discharge device.

In other words, the battery cell is discharged to such an extent that the rest voltage of the battery cell falls below the limit value for the safety of the battery _cell U _{min_safety} (the second limit value for the battery _{cell voltage} ). In this case, the rest voltage of the battery cell is determined by means of the battery state detection and prediction (state determination device). From this rest voltage, the copper of the current collectors and the carrier foil of the anode can decompose electrochemically in a lithium-ion battery cell. If the battery cell is recharged after such a decomposition, dendrites can form, which can lead to an internal short circuit of the battery cell. In this case, the current bypass is permanently activated by means of the deep discharge function according to the invention. The battery cell can thus not be discharged further. By means of the deep discharge function, the battery cell can optionally also be deeply discharged via the discharge device (discharge system) until it has reached a voltage of 0 V electrochemically. The battery cell is then also deactivated electrochemically and then has the most stable possible state with regard to their safety. Depending on the requirements for the availability of the battery cell or of the battery system in which the battery _cell is used, the depth discharge safety function can be modified such that a drop _below the voltage U _{min_safety is} possible for a certain time and up to a certain limit.

The advantage here is that a battery cell by means of the invention, in particular integrated in the battery cell depth discharge safety function all necessary measures for avoiding deep discharge or for the safe handling of the situation in which a deep discharge occurs, can perform themselves and not on the functionality of a parent Battery management system is instructed.

Optionally, the intrinsically safe battery cell or the battery cell device according to the invention comprise an additional electronics (voltage adjustment device), by means of which the output voltage of the battery cell can be switched such that the battery cell voltage in positive orientation or the battery cell voltage in negative orientation or a voltage of at the battery cell terminals (output terminals) 0 V can be applied.

The method according to the invention preferably comprises the functional features of the battery cell device according to the invention individually or in combination.

Preferably, in the method according to the invention, the critical battery cell state in which the battery cell can be damaged by a deep discharge, in the presence of an amount of the battery cell voltage detected by the sensor device and / or an amount of battery cell arrest voltage and / or a battery cell charging state, each having a first corresponding limit reaches or falls below, determined by means of the state determining device.

Furthermore, in the method according to the invention, preferably the critical battery cell state in which the battery cell can be damaged by a deep discharge, in the presence of an amount of detected by the sensor device battery cell voltage and / or an amount of battery cell arrest voltage and / or a battery state of charge, each one against the first corresponding limit value smaller second corresponding limit value, determined by means of the state determining device. For the transfer of the battery cell into the deep discharge operating mode in the presence of the critical battery cell state, the battery cell is preferably completely discharged via an unloading device arranged in the battery cell device and activated by means of the actuator device.

A further aspect of the invention relates to a battery system with a battery which comprises a plurality of battery cell devices according to the invention and a battery management system which is designed to communicate with the monitoring devices arranged in the battery cell devices.

The invention also relates to a vehicle with a battery system according to the invention.

Brief description of the drawings

Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings. In the drawing is:

1 the block diagram of a known from the prior art battery system with a traction battery,

2 FIG. 2 is a diagram illustrating the failure mechanisms of a prior art lithium-ion battery that may cause thermal cycling of this lithium-ion battery. FIG.

3 3 is a block diagram of a battery system known from the prior art with a traction battery formed from a plurality of battery cells and a battery management system;

4 the schematic diagram of a battery cell device according to a first embodiment of the invention,

5 a flowchart of a model-based state determination and prediction, with which the detection and / or prediction of a battery cell state according to the invention can be performed, according to an embodiment of the invention, and

6 a flowchart of a security functionality of an intrinsically safe battery cell, which is equipped with the deep discharge safety function according to the invention.

Embodiments of the invention

In the 4 is the schematic diagram of an intrinsically safe battery cell device 221 illustrated according to a first embodiment of the invention. The electrically intrinsically safe battery cell device 221 includes a battery cell 21 , in particular a lithium-ion battery cell, and a monitoring device (monitoring electronics) for monitoring the battery cell 21 , The monitoring device comprises a sensor device (sensor system) 240 for detecting physical quantities for determining the state of the battery cell, a state detecting device 250 (Battery cell state detection and prediction), which from the sensor signals the current battery cell state 21 especially in terms of their safety and also recognizes the future behavior of the battery cell 21 predict or predicate, and an actuator device (safety actuator) 260 with which the battery cell 21 can be converted into a safe mode of operation upon detection of a critical battery cell state.

In this case, the sensor device 240 configured to detect and monitor the battery cell voltage and further to detect a current flowing through the battery cell, a battery cell temperature, and a battery cell internal pressure. Furthermore, the sensor device 240 adapted to a linear acceleration and / or a rotational acceleration of the battery cell 21 capture.

In the battery cell device 221 a discharge device (not shown separately) may be arranged, which by means of the actuator device 260 can be activated. The discharge device is intended, in an activated discharge mode, the battery cell 21 by means of moderate discharge currents and / or in an activated fast discharge mode to discharge the battery cell by means of high discharge currents near the short-circuit current.

Furthermore, in the battery cell device 221 a current bypass (not shown separately) arranged by means of the actuator device 260 can be activated and is designed, in the activated state, between the battery cell terminals (output terminals) 222 . 223 to redirect the flowing current of both polarities via a battery cell external current path.

Further, in the battery cell device 221 Safety functions, in particular a deep discharge safety function 270 , integrated, by the monitoring device are provided and the battery cell 21 can be immediately transferred to a safe operating mode in the presence of a critical or critical battery cell state. In the presence of a critical battery cell state in which the battery cell 21 can be damaged by a deep discharge, transforms the deep discharge safety function 270 through the actuator device 260 the battery cell 21 in a safe deep discharge mode of operation in which the battery cell 21 can not be discharged further, or completely discharged.

For the deep discharge safety function, the actuator device (safety actuator) must 260 can switch the current bypass, in which between the battery cell terminals (output terminals) 222 . 223 An electric current can flow without passing this current through the electrochemical part of the battery cell 21 flows. Not absolutely necessary for the present depth discharge safety function, but for the realization of an overall intrinsically safe battery cell or battery cell device 221 preferably necessary, is the possibility of the battery cell 21 to discharge via the discharge device (Discharge Device).

Optionally, the monitoring device comprises the battery cell device according to the invention 221 a tension adjusting device (switching actuator) 280 , which is adapted to the output voltage of the battery cell 21 to switch such that the battery cell 21 at the battery cell terminals 222 . 223 the battery cell voltage in positive orientation (+ U _{battery cell} ) or no voltage (0 V) or the battery cell voltage in negative orientation (-U _battery cell) can deliver. Simply put, the output voltage of the battery cell 21 by means of the tension adjustment device 280 be switched to the voltage values + U _{battery cell} , 0 V and possibly also -U _battery cell.

When in the 4 illustrated battery cell device according to the invention 221 that, when the monitoring electronics according to the invention in the battery cell 21 is integrated, is referred to as intrinsically safe battery cell, the overcharge safety devices (OSDs) used so far and battery cell fuses (cell fuses) can be omitted and the measures used to increase the safety of mechanical deformation or penetration measures, such as equipping the battery cells with a Nail Penetration Safety Device (NSD), either also omitted or at least made much easier, since much lower demands are made on these measures. This represents a significant improvement over the prior art. The UN transport tests are for the battery cell device according to the invention 221 or for the intrinsically safe battery cell 21 that is for the battery cell 21 with the associated sensor device (sensors) 240 and actuator device (safety officer) 250 carried out. The battery cell 21 may then only together with the associated sensor device (sensors) 240 and actuator device (safety officer) 25 , be transported. That means the battery cell 21 only as one in the battery cell device 221 arranged battery cell 21 or may be transported as an intrinsically safe battery cell with integrated monitoring electronics.

With such battery cell devices according to the invention, each such as those in the 4 shown battery cell device 221 are formed, battery systems can be constructed in which much lower demands are placed on the associated battery management system. The electronics of such a battery management system can then probably be developed with the usual quality assurance measure (ASIL classification QM) and does not have to meet ASIL C.

The battery cell devices according to the invention, each such as those in the 4 shown battery cell device 221 are not trained on the use of lithium-ion battery cells 21 limited and can also be used for other battery cell technologies, such as nickel-metal hydride battery cells.

In the 5 the flowchart of a model-based state determination and prediction is shown, with which the detection and / or prediction of a battery cell state according to the invention can be performed. The state determination 510 gets on a battery 20 performed in which a plurality of battery cell devices according to the invention 221 can be arranged. The state determination 510 is by the state detection device according to the invention 250 which acts as an observer and a battery model 507 implemented with parameter adaptation. As in 5 is shown receives the battery model 507 current readings of different, the battery 20 relevant physical quantities. These include in particular a current battery _cell current I _Batt , a battery cell _temperature T _Batt , and a battery cell _{internal pressure} P _Batt . The state determination device uses the battery model 507 a current battery condition determined. The battery model 507 and the condition determined from this are constantly checked on the basis of current measured values. For example, a model-based battery cell voltage U _{Mod can be} compared with a measured current battery voltage U _Batt . Based on the comparison and one The deviation detected may be the applied battery model 507 be adjusted accordingly.

The battery model also provides estimates or calculated values of state of charge (SOC) 501 , an aging condition (SOH) 502 , and a security condition 503 for processing in the context of battery condition prediction 511 as input to another battery model 509 be passed with state prediction. The battery state prediction also receives additional information relevant to the accuracy of the prediction 508 , which include in particular load profiles and boundary conditions. For example, the information may contain stored values with the time profile of a charging current I (t), which as another parameter in the further battery model 509 incorporated. With the help of the further battery model 509 will then be the input data 501 . 502 . 503 , I (t) processes and forecasts output. In particular, predictions about battery performance are made 504 about in the battery 20 stored energy 505 , the functional state (SOF) 506 the battery 20 , and / or the predictable safety condition 503 the battery 20 met. In this way, the predictable security state 512 or the current security status 503 Provide information about whether a normal operating condition of the battery 20 present, or if the battery 20 is in a critical condition.

The 6 shows a flowchart of a security functionality of an intrinsically safe battery cell, with the deep discharge safety function according to the invention 270 Is provided. According to the in 6 In the embodiment shown, the battery cell 21 In normal operation, only be discharged to the extent that the voltage of the battery cell 21 reaches the lowest limit value U _min permissible according to the specification. This is in particular from the in 6 shown diagrams 601 and 602 to see. This is done according to the diagram 601 a logical 1 to an AND gate 606 if the battery cell voltage U is below the value U _min , otherwise a logical 0 is output. Further, according to the diagram 602 a logical 1 to the AND gate 606 output if the battery cell current I would be less than 0 and therefore a discharge current. Overall, then a temporary activation 604 of the current bypass, if the battery cell 21 at low voltage less U _min would be further discharged. This will be the battery cell 21 do not discharge further. However, if the battery cell current I is greater than 0 and thus a charging current, or if the voltage is greater than or equal to U _min , the current bypass is disabled again. The battery cell 21 will be charged again.

Alternatively, the deep discharge safety function 270 also for the state of charge SOC of the battery cell 21 or the rest voltage U _{00 of} the battery cell 21 be performed. These state variables of the battery cell 21 are doing so with the help of battery condition detection 250 determined.

The described method preferably only applied as long as the battery _cell voltage U _{cell of} the battery _cell 21 is in a range U _{min_safety} <U _cell <U _min , that is, as long as the battery _cell voltage U _cell is below U _min , but has not yet reached a safety-relevant voltage _value U _{min_safety} . The quiescent voltage of the battery cell 21 is doing with the help of the battery state detection or the state detection device 250 determined. Has the battery cell 21 Once it has _fallen below the value of U _min , it can drop, for example, by its very long storage without charging by the self-discharge, which typically makes up about 1% -3% per month, in their voltage so that it _falls below the said limit U _{min_safety} . See also the diagram 603 in 6 , From this _lower voltage _limit U _{min_safety} , the copper of the current collectors and the carrier foil of the anode can electrochemically decompose in a lithium-ion battery cell. If the cell is recharged after such a decomposition, dendrites may form, which can lead to an internal short circuit of the cell. Therefore, in this case, the current bypass is permanently activated, which in the 6 by the reference numeral 605 referred to as. The cell can thus not be further discharged.

Optionally, the battery cell 21 , whose voltage U _{cell has} already reached the lower value of U _{min_safety} , are further deep-discharged via the Discharge Device until it has reached the voltage 0 V electrochemically. The battery cell 21 is then also deactivated electrochemically and then has the most stable possible state in terms of safety. Depending on the requirements of the availability of the battery cell or the battery system in which the battery cell is used, the depth discharge safety function 270 be modified so that for a certain time and up to a certain limit also _{falls below} the voltage U _{min_safety} .

According to the invention, the battery cells or battery modules are controlled such that their operating parameters are within the respective limits which are necessary for safe operation.

Thus, lithium-ion battery cells typically within a voltage range Umin to Umax from 2.8 V to 4.2 V, or preferably 3, Operated from 0 V to 4.2 V volts. This applies in particular to safety-relevant values U _{min_safety} or U _{max_safety} . However, these specifications apply to the voltages to be measured U battery cell at idle, that is, when no current flows through the battery cell. It is important to observe these limits, otherwise the electrodes may be damaged.

The open circuit voltage of the battery cells depends essentially on their state of charge. In this case, typically a charge state SOC of 0%, at 3.5 V a charge state of 20%, and at 4.2 V a state of charge of 100% is assumed for a voltage U battery cell of 2.8 V, these values being in each case of type and Material of the cathode, the anode, and / or the electrolyte used.

When a current flows through a battery cell, the battery cell voltages UBatteriezelle may differ from the above figures. Suppose the open circuit voltage is 3.5 V and the internal resistance of the battery cell at 25 ° C is 10 mΩ. At a charging current of 100 A, this would then give a voltage value U battery cell of 3.5 V + 1.0 V = 4.5 V. The internal resistance of the battery cell can be as high as 50 mΩ, for example, at a temperature of 0 ° C For example, for an exemplary discharge current of 50A, a voltage would be U battery cell of 3.5V minus 2.5V = 1.0V. Due to the applied control and the sensors used, these voltage values are not reached at room temperature or at 0 ° C. Generally, during operation of the battery cells, the Umax value may be between 4.2V and 5.0V and the Umin value between 1.5V and 4.2V, preferably between 1.8V and 4.15V Values, however, do not refer to the open circuit voltage.

The above voltage values apply to a single battery cell. For a battery module, it depends on how many cells are connected in series or in parallel. Thus, the allowable module open circuit voltage UBatteriemodul is between n × 2.8V to n × 4.2V, where n is the number of battery cells connected in series.

Limits for temperatures in lithium-ion battery cells are approximately at Tmin = -40 ° C and Tmax = 30 ° C to 50 ° C, preferably 30 ° C to 45 ° C, most preferably 35 ° C to 40 ° C. For safety reasons, a maximum temperature Tmax-safety of 46 ° C to 80 ° C, preferably 50 ° C to 60 ° C should not be exceeded. Furthermore, the maximum outdoor temperature Taußen, at which the battery cells are operated, should not exceed 40 ° C.

The battery currents through the battery cells should not be outside a range of -1000 A to +1000 A, preferably -600 A to +600 A, more preferably -500 A to +500 A, even more preferably -450 A to +450 A, and more preferably -350 A to + 350 A, are.

The internal pressure of a battery cell should not leave the pressure range of 2 bar to 8 bar, preferably 3 bar to 7 bar.

The above discussion has been made by way of example for lithium-ion battery cells or lithium-ion battery modules, the values given in particular for lithium-ion battery cells with lithium manganese cobalt oxide as active material for the cathode. However, the invention is not limited to such battery cells, in particular not to lithium-ion battery cells. In practice, the numerical values of the operating parameters to be selected thus depend on the particular battery cell type.

In addition to the above written disclosure is hereby further disclosure of the invention supplementary to the representation in the 1 to 6 Referenced.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• ISO 26262 [0019]

Claims (10)

Battery cell device ( 221 ) with a battery cell ( 21 ) and a monitoring device for monitoring the battery cell ( 21 ), characterized in that the monitoring device comprises a sensor device ( 240 ) for detecting a plurality of the battery cell ( 21 ), a state determining device ( 250 ), which is designed to be evaluated on the basis of a particularly model-based evaluation by the sensor device ( 240 ) to recognize and / or predict a current and / or future battery cell state, and an actuator device ( 260 ) adapted to transfer and / or maintain the battery cell from a critical and / or critical battery cell state to a safe operating mode comprises, and preferably a deep discharge safety function ( 270 ) by means of the state determining device a critical battery cell state in which the battery cell ( 21 ) can be damaged by a deep discharge, can be determined and the battery cell ( 21 ) in the presence of the critical battery cell state by the actuator device ( 260 ) into a deep discharge operating mode designed as a safe operating mode, in which the battery cell ( 21 ) can not be further discharged or completely discharged, transferred and / or held. Battery cell device ( 221 ) according to claim 1, wherein the sensor device ( 240 ) is adapted to detect the battery cell voltage and / or to monitor the presence of a battery cell voltage whose magnitude is in a predetermined battery cell voltage range, and / or by the battery cell ( 21 ) and / or a battery cell temperature and / or a battery cell internal temperature, in particular a battery cell winding temperature and / or a battery cell outer temperature, and / or a battery cell internal pressure and / or a linear acceleration of the battery cell ( 21 ) and / or a rotational acceleration of the battery cell ( 21 ) and / or the actuator device ( 260 ) is adapted to transfer the battery cell ( 21 ) into the safe operating mode and / or to hold the battery cell ( 21 ) in the safe operating mode, one in the battery cell ( 21 ) arranged to enable discharging device, which is provided, in an activated discharge mode, the battery cell ( 21 ) by means of a predetermined discharge current and / or in an activated fast discharge mode, the battery cell ( 21 ) by means of a discharge current which is a predetermined fraction of a short-circuit current of the battery cell ( 21 ), and / or one in the battery cell device ( 221 ) arranged current bypass ( 604 . 605 ), which is intended, when activated, to switch between the battery cell terminals ( 222 . 223 ) to redirect current flowing through a battery cell external lying current path. Battery cell device ( 221 ) according to claim 2, wherein the state determining device ( 250 ) is adapted to the critical battery cell state in which the battery cell ( 21 ) can be damaged by a deep discharge, in the presence of an amount of the battery cell voltage and / or an amount of battery cell arrest voltage and / or a battery cell charging state, each of which reaches or falls below a first corresponding limit and / or smaller than the first corresponding threshold and in particular in dependence of the requirements for the availability of the battery cell ( 21 ) set to determine the second corresponding limit value, and / or the Aktorvorrichtung ( 260 ) is designed to transfer the battery cell ( 21 ) in the deep discharge operating mode in the presence of the critical battery cell state the current bypass ( 604 . 605 ) in a state in which by the battery cell ( 21 ) a discharge current would flow, activate and the current bypass ( 604 . 605 ), in another state in which by the battery cell ( 21 ) a charging current can flow, to disable. Battery cell device ( 221 ) according to one of claims 2 or 4, wherein the state determining device ( 250 ) is adapted to the critical battery cell state in which the battery cell ( 21 ) can be damaged by a deep discharge, in the presence of an amount of the battery cell voltage and / or an amount of battery cell arrest voltage and / or a battery state of charge, which in each case falls below the second corresponding limit, to determine and / or the Aktorvorrichtung ( 260 ) is designed to transfer the battery cell ( 21 ) in the deep discharge mode in the presence of the critical battery cell state, the current bypass ( 604 . 605 ) permanently activate and / or activate the unloading device. Battery cell device ( 221 ) according to one of the preceding claims, wherein the battery cell device comprises a voltage setting device, which is designed to adjust the battery cell voltage applied to the output terminal of the battery cell device during the normal operating mode such that a battery cell voltage in positive or negative orientation is applied to the battery terminals or the battery cell is connected to the battery cell Output terminals outputs a voltage of 0V. Method for monitoring a battery cell device ( 221 ) arranged battery cell ( 21 ) by means of a battery cell device ( 221 ) arranged monitoring device, characterized in that a plurality of physical quantities for determining a battery cell state by means of a monitoring device arranged in the sensor device ( 240 ), a current and / or future battery cell state by means of a state-determining device arranged in the monitoring device on the basis of a particularly model-based evaluation of the state of the sensor device ( 240 ) detected and / or predicted, in the presence of a critical and / or critical battery cell state, the battery cell ( 21 ) by means of an actuator device arranged in the monitoring device ( 260 ) is transferred into a safe operating mode, and the monitoring device preferably provides a deep discharge safety function, by means of which the occurrence of a critical battery cell state in which the battery cell ( 21 ) can be damaged by a deep discharge, by the state determining device ( 250 ) is determined, and in the presence of the critical battery cell state, the battery cell ( 21 ) by the actuator device ( 260 ) in a deep discharge mode designed as a safe operating mode, in which the battery cell ( 21 ) is not further unloaded or completely unloaded, transferred and / or held. The method of claim 6, wherein the critical battery cell state in which the battery cell ( 21 ) can be damaged by a deep discharge, in the presence of an amount of the means of the sensor device ( 240 ) detected battery cell voltage and / or an amount of the battery cell arresting voltage and / or a battery cell charging state, which in each case reaches or falls below a first corresponding limit, by means of the state determining device ( 250 ) is determined. Method according to claim 7, wherein the critical battery cell state in which the battery cell ( 21 ) can be damaged by a deep discharge, in the presence of an amount of the battery cell voltage detected by the sensor device and / or an amount of the battery cell arrest voltage and / or a battery state of charge which in each case falls below the first corresponding limit value smaller second corresponding limit value, by means of the state determining device ( 250 ) is determined and / or for the transfer of the battery cell ( 21 ) in the deep discharge operating mode in the presence of the critical battery cell state, the battery cell ( 21 ) via a in the battery cell device ( 221 ) and by means of the actuator device ( 260 ) activated unloading device is completely discharged. Battery system with a battery containing several battery cell devices ( 221 ) according to one of claims 1 to 5, and a battery management system, which is designed to be connected to the battery cell devices (in 221 ) arranged to communicate monitoring devices. Vehicle with a battery system according to claim 9.

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